ABOUT THE COVER: GREEN HERON

The Green Heron (Butorides virescens) is a relatively small, dark, compact bird. It is generally shy, but its skeow flight call when disturbed is familiar to anyone who has flushed one, and its habit, when flushed, of producing a stream of white defecation has produced some interesting monikers including "shite- polk" and "chalk-line." Adult Green Herons are readily distinguished by their greenish-black cap and back, buff-tipped blackish wing feathers, and rufous necks. Females are generally duller in plumage than males, but this is not a reliable field character. Young birds are striped with brown on neck and underparts and have a brownish, buff-spotted back. Green Herons fly with neck and head retracted with slow steady wingbeats. The shifting tides of lumping and splitting species and subspecies are well illustrated by the ongoing debate over the taxonomic status of the Green Heron. Long considered a separate species, the Green Heron was lumped with the Green-backed Heron, to become B. striatus virescens, one of 30 subspecies with worldwide distribution. In 1993 based on much the same evidence that had produced the lumping, the tide of analysis shifted once again, and we got our Green Heron back as a full species. Four subspecies of the Green Heron are currently recognized (as many as eighteen were recognized early in this century!). The breeding range of the Green Heron extends from southern Canada south over the eastern half of the United States down through coastal Mexico and Central America wherever there is suitable wet habitat. A western population breeds from California south through Panama. Green Herons are fairly common spring migrants in Massachusetts, arriving in late April and May. They are most common in August during the post-breeding dispersal (as many as sixty-four were reported from a Westborough swamp), and they depart Massachusetts by early October. Green Herons are monogamous breeders, either as solitary pairs or in loose colonial aggregations. They prefer swampy thickets, stream edges, and sloughs, but also nest in salt-marsh thickets, often on islands. They are not rigid in their nesting habitat requirements and may nest in dry woods or orchards if suitable foraging habitat is nearby. They utter a wide variety of calls during the breeding season: harsh hostile raah-raah calls, a series of ku-ku-ku calls when disturbed, a show-ch advertising call, and a sheow alarm call. Skewing calls may accompany pursuit and circle display flights during courtship. Some of the display flights involve exaggerated crook-necked and flapping flights with legs dangling. A wide assortment of hostile and nuptial displays featuring bulging eyes, erect plumes, and exaggerated postures accompany the various aspects of the breeding cycle.

BIRD OBSERVER 131 Vol. 24, No. 2, 1996 Green Heron Illustration by Julie Zickefoose

In Massachusetts nesting occurs during May and June. Nests are usually placed over water in a wide variety of trees and shrubs, usually with the nest hidden and shaded by dense foliage. The nest site is highly variable, however, and nests may be placed on the ground. The nest usually is a platform of sticks without lining. Males select the nest site and gather sticks for the female to work into the nest. They may reuse old nests of their own or other species. The clutch is three to five pale blue-green eggs. The parents share incubation duties for the three weeks until hatching. The young can fly after about three weeks, and are probably independent by four to five weeks of age. Both parents feed the young which may be left unattended after about ten days. When unattended, the young may adopt the bill-pointing-to-the-sky bittern stance, and utter an incessant tik- tik-tik-tik-tik food begging call when a parent bird returns. Green Herons forage mostly from a crouched posture with head and neck retracted, darting the head forward and grasping or spearing fish, which are their main food item. They are cryptic feeders, standing or walking slowly in shallow water, although they have been reported to use fifteen of the thirty-six described heron foraging behaviors including plunging into water, and may fish from

BIRD OBSERVER 132 Vol. 24, No. 2, 1996 perches on low limbs or rocks. Although they usually prefer secluded foraging spots, they will forage on mud flats and may forage at any time during the day or night. They have relatively large bills and hence may take larger prey items such as frogs. Their most interesting foraging behavior is bait fishing, which makes them one of the few tool-using birds. They have been observed dropping crusts of bread, mayflies, feathers, twigs, leaves, berries, insects, and plastic foam bits into the water and catching the fish that rise to the bait. The cover drawings illustrate a Green Heron baiting fish, and the drawing on the previous page shows the culmination of this effort with the heron and its captured fish. Like human fisherman, they generally have the best results using live bait! Green Herons are largely fish eaters (piscivorous) but will take a wide spectrum of small vertebrates and invertebrates when opportunities arise. Population changes over time are difficult to assess because of the cryptic behavior of the species, but habitat destruction (e.g., draining swamps for agriculture) has probably reduced local populations. Increased recreational use of river channels, ponds, and lakes may also have a negative impact on local populations, and Green Herons may still be subject to predator control at some fish hatcheries. At the present time, however. Green Herons are increasing their range in many parts of North America and have largely escaped the depredations caused by DDT and other persistent pesticides in some heron species. Despite their generally cryptic behavior. Green Herons seem to tolerate human disturbance reasonably well and sometimes nest in urban areas. Good luck to the Mount Auburn Cemetery pair this spring! W. E. Davis, Jr.

ABOUT THE COVER ARTIST

Julie Zickefoose is an artist, writer, and naturalist who is devoted to the study, conservation, and appreciation of nature. Educated at Harvard University in biology and art, Julie worked six years as a field biologist for The Nature Conservancy before turning to full-time freelance art. She contributes regularly to magazines from Ladybug to Bird Watcher's Digest, for which she is a contributing editor. Book illustration credits include the Academy of Natural Sciences, for which she is contributing illustrations to the multi-volume work The Birds of North America. Julie has shown her work at Harvard University, the National Zx30 , the Leigh Yawkey Woodson Art Museum, and the XIX International Ornithological Congress. She also sings and plays in a band. The Swinging Orangutangs, whose members include her husband. Bill Thompson III, editor of Bird Watcher's Digest. Julie can be reached at Indigo Hill Arts, Route 1, Box 270, Whipple, Ohio 45788. M. Steele

BIRD OBSERVER 133 Vol. 24, No. 2, 1996